-LRB- CNN -RRB- -- If you use mobile data services outside your wireless carrier 's network coverage area , you could get a nasty surprise in your bill .

Data-roaming charges can be outrageously expensive , even totaling thousands of dollars in a single month . Also , carriers often do n't make it obvious to phone users when and where data-roaming fees might apply , or how fast they can add up .

But that could be changing . At its December open meeting , the Federal Communications Commission may vote on a proposed rule that would mandate automatic data-roaming agreements between carriers and address consumer worries by requiring reasonable prices for this service .

In April , the FCC ordered all wireless carriers to automatically allow voice calls to roam across networks . The data-roaming proposal would do the same for data traffic , i.e. mobile Web surfing , running apps and other actions .

The stakes here are much higher than just data-roaming charges . Network neutrality -- the contentious principle that broadband providers should maintain equal Web access to all and not offer favorable delivery speeds to certain clients -- may be at stake with this vote .

Recently , Politico 's Kim Hart explained : `` The debate is the latest skirmish in the larger battle over broadband reclassification . To impose the rule , the FCC would need to change the legal framework that governs broadband services -- an idea pushed by net neutrality advocates but vehemently opposed by many Republicans and internet providers . ... Enacting a data-roaming rule would be politically expedient for FCC Chairman Julius Genachowski , who has faced legal setbacks in his quest to make wireless networks more open . ''

The two largest U.S. carriers -- Verizon and AT&T , which together serve over 60 percent of U.S. mobile subscribers -- strenuously oppose this move . These carriers claim they already have negotiated dozens of data-roaming agreements with smaller carriers .

According to Fierce Wireless , `` The arguments by the nation 's largest operators stand in stark contrast to filings by smaller wireless carriers , which argue the FCC should mandate automatic data roaming as it has already done with voice calling -- an effort intended to give smaller carriers a chance to compete against larger operators . ''

The carriers also have a more fundamental objection to the proposed data-roaming rule : They claim the FCC does not have the authority to regulate the data side of their business .

Taking the carriers ' side against the FCC in this fight are some powerful politicians -- most notably Florida congressman Cliff Stearns , the ranking Republican on the House Communications , Technology and the Internet Subcommittee . Stearns may take over leadership of the powerful House Energy and Commerce Committee when Republicans gain control of the House in 2011 .

Earlier this month , when rumors began circulating that the FCC might move to vote on data roaming , Stearns issued a a statement opposing the vote .

`` Ramming through internet regulations would ignore the will of a bipartisan majority of Congress and the American public , '' he said . `` It would further impede economic growth and job creation . ''

The FCC sidestepped this vote in the agenda for its November 30 open meeting . Without explanation , the agency last week announced it will delay its December meeting by a few days , until December 21 .

The agenda for the December FCC open meeting has not yet been published . If a vote on the data-roaming proposal appears on that agenda , the FCC might be able to get this rule approved under the wire , increasing its ability to pursue its net neutrality plans , before a more hostile Congress moves in .

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The FCC may be prepared to vote on a proposed rule that could limit wireless data-roaming charges

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The rule would mandate automatic data-roaming agreements between carriers

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It would also address consumer worries by requiring reasonable prices for this service